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Synthetic oligosaccharides are objects of interest as model compounds in studies on the biological activity of natural compounds, but also as components for new drugs, glycoconjugate vaccines, carbohydrate diagnostic agents and various other products. The key stage in oligosaccharide synthesis is the glycosylation reaction, which leads to the formation of a linkage between carbohydrate fragments. This review highlights a current problem in modern glycochemistry – the methods of stereocontrol in the glycosylation reaction. Protecting groups within the structure of glycosyl donors are considered as stereocontrolling factors, affecting the reaction mechanism by means of (1) participation or anchimeric assistance, (2) deactivation, (3) intramolecular aglycone delivery. The well-established mechanism of neighboring group participation at O-2 for the synthesis of 1,2- trans glycosides is shown, as well as its modern modifications, including activating ethers, chiral protecting groups and achiral bicyclic glycosyl donors. The mechanisms of remote participation from O-3, O-4 and O-6 of the glycosyl donor are discussed in detail. In addition, approaches to stereocontrol using deactivating protection (conformation constraining and electron withdrawing groups) are described. Finally, synthetic approaches based on intramolecular aglycone delivery are considered. Both classical and novel protecting groups used to control the steric outcome of glycosylation are presented, the mechanisms underlying the presented approaches are discussed in detail, while also showing how the described strategies apply to the synthesis of complex structures. [ABSTRACT FROM AUTHOR]

We studied carbohydrate specificity and isotypes of antibodies to BSA-conjugated tetrasaccharide, a repeating unit of the capsular polysaccharide of Streptococcus pneumoniae serotype 14, in mouse polyclonal sera and hybridoma-synthesized products. Natural IgM antibodies to the tetrasaccharide containing epitopes similar to surface carbohydrate structures of mammalian and human cells in low titers were determined in native mouse serum by ELISA using biotinylated tetrasaccharide and synthetic capsular polysaccharide as the solid-phase antigens. Polyclonal sera to the conjugated tetrasaccharide contained IgM and all subclasses of IgG antibodies, which were detected in a higher titer when the biotinylated tetrasaccharide was used as a solid phase antigen compared to synthetic capsular polysaccharide. Monoclonal antibodies to S. pneumoniae serotype 14 tetrasaccharide were identified in an equivalent titer using either biotinylated tetrasaccharide or synthetic capsular polysaccharide. Monoclonal antibodies obtained in vitro belonged to IgM isotype and cross-reacted with secondary full-size IgG antibodies. In the serum of mice inoculated with hybridoma, IgM and IgG2a antibodies recognizing the tetrasaccharide epitope in the structure of synthetic capsular polysaccharide were simultaneously determined. [ABSTRACT FROM AUTHOR]

Abstract: Laboratory animals (the California rabbit) were immunized with natural preparations of Saccharomyces cerevisiae and Candida krusei yeasts. The resulting sera have been analyzed with ligand libraries constructed from synthetic oligosaccharides related to the main carbohydrate components of the fungal cell wall. It is shown that the antibodies in the studied sera predominantly recognize mannan fragments, with the carbohydrate specificity profile being different for S. cerevisiae and C. krusei. Sera against S. cerevisiae contained antibodies that recognize β-glucan, and the minimal recognizable epitope is linear trisaccharide. These results are necessary for the creation of needed immunoenzyme diagnostics for the detection and species characterization of fungi. [ABSTRACT FROM AUTHOR]

Brush rabbits were immunized with injections prepared from the fungi Aspergillus fumigatus, Aspergillus niger, and Aspergillus repens. A library of synthetic biotinylated oligosaccharides containing the key fragments of antigenic polysaccharides of the fungal cell wall—galctomannan, α- and β-glucans, mannan, and chitin—was used to analyze carbohydrate specificity. The anticarbohydrate antibodies obtained from animals immunized with preparations from A. fumigatus and A. repens predominantly recognized epitopes containing galactofuranoside residues, while the majority of the antibodies against A. niger bound the chitooligosaccharide ligand. These results are the basis for the identification of specific markers required for the development of immunoenzyme test systems. [ABSTRACT FROM AUTHOR]

The carbohydrate specificity of antibodies obtained by immunizing laboratory animals with immunogens prepared from the Aspergillus fumigatus cell wall was analyzed using the library of biotinylated synthetic oligosaccharides. It has been shown that the main part of antipolysaccharide antibodies recognizes galactomannan in the studied immunogens with preference to its fragments containing more than two β-(1→5)-linked galactofuranosyl units. The data obtained can form the basis for the development of enzyme immunoassay for the detection of this dangerous fungal pathogen. [ABSTRACT FROM AUTHOR]

The electrospray ionization high-resolution mass spectra of biotinylated hexaethylene glycol-spacered molecular probes bearing biologically relevant carbohydrate moieties in positive and negative modes were recorded and interpreted. Collisionally induced decay mass spectra (positive mode) revealed different patterns depending on the charge of the parent ion, attached cations (or ions), the composition, and the sequence of carbohydrate fragments. The most intense peaks (two series) originated from the sequential cleavage of glycoside bonds resulting in charge location on the reducing end (Y series observed for all of the test compounds) or nonreducing end (B series). Hexaethylene glycol chain fragmentation giving rise to the cleavage of the C-O bond remote from the biotin moiety was observed. Other fragment ions lighter than the above by a difference of (C2H4O)n were absent or much smaller. Similar fragmentation was found for all of the nonsulfated biotinylated glycosides with the hexaethylene glycol spacer thus demonstrating that this type of fragmentation was characteristic of such molecular probes. Similar cleavages along with biotin moiety decay via the elimination of H2S and H2CS were observed for negative ions in the collisionally induced decay mass spectra of sulfated and neutral molecular probes. [ABSTRACT FROM AUTHOR]

Review: 111 refs. [ABSTRACT FROM AUTHOR]

Review: 107 refs. [ABSTRACT FROM AUTHOR]